The traditional implantable cardiac pacemaker includes a pulse generator device to which one or more flexible elongate lead wires are coupled. The device is typically implanted in a subcutaneous pocket, remote from the heart, and each of the one or more lead wires extends therefrom to a corresponding electrode, coupled thereto and positioned at a pacing site, either endocardial or epicardial. Mechanical complications and/or MRI compatibility issues sometimes associated with elongate lead wires are well known to those skilled in the art and have motivated the development of cardiac pacing devices that are wholly contained within a relatively compact package for implant in close proximity to the pacing site, for example, within a right ventricle RV of the heart. With reference to FIG. 1, such a device 100 is shown, having been deployed by an exemplary delivery system 200 at an implant site in the right ventricular apex.
FIG. 1 illustrates device 100 including a hermetically sealed enclosure 105 containing pulse generator electronics and a power source (not shown), pace/sense electrodes 111, 112 formed on an exterior surface of enclosure 105, and a fixation member 115, which is mounted to a distal end of enclosure 105, in proximity to electrode 111, in order to fix, or secure electrode 111 against the endocardial surface at the implant site. Enclosure 105 is preferably formed from a biocompatible and biostable metal such as titanium overlaid with an insulative layer, for example, medical grade polyurethane or silicone, except where electrode 112 is formed as an exposed portion of the metal. A hermetic feedthrough assembly, such as any suitable type known to those skilled in the art, couples electrode 111 to the pulse generator contained within device enclosure 105. FIG. 1 further illustrates a proximal end 121 of device enclosure 105 configured for temporary attachment of a tether 280, or some other type of retention member, that may be employed to test the engagement of fixation member 115 with tissue at the implant site, and/or to retain a temporary connection between the deployed medical device 100 and delivery system 200, if repositioning of device 100 is necessary.
FIG. 2A is a plan view of exemplary delivery system 200; and FIGS. 2B-C are plan views of exemplary outer and inner assemblies, respectively, of system 200. FIG. 2A illustrates system 200 including a handle 210 from which the elongate outer assembly of FIG. 2B extends. FIGS. 2A-B illustrate the outer assembly including an elongate outer tube 230, which has a proximal end 231 coupled to a first control member 211 of handle 210, and a stability sheath 250, which surrounds a limited length L of outer tube 230 and is fixed to handle 210. FIG. 2C illustrates the exemplary inner assembly, which extends within a lumen formed by outer tube 230 of the outer assembly in system 200; the inner assembly includes an elongate inner member 220, wherein inner member 220 includes a proximal end 221, which is fixed within handle 210, and a flared distal end 222, which is configured to conform to proximal end 121 of device 100. With reference to FIG. 2A, proximal end 221 of inner member 220 may be coupled to a stop cock 260 by a luer fitting (not shown), and distal end 222 of inner member 220 is contained in a distal-most portion 232 of outer tube 230, just proximal to a distal opening 203 thereof. With reference to FIG. 2D, which is a plan view of the distal end of system 200 having a cut-away section of outer tube 230, distal-most portion 232 is sized to contain device 100 therein, when proximal end 121 of device 100 abuts flared distal end 222 of inner member 220. FIG. 2C further illustrates the inner assembly including a pull wire 225, which is coupled to a second control member 212 of handle 210, at a proximal end 51 thereof, and which is anchored at a location 52, in proximity to distal end 222 of inner member 220, so that inner member 220 may be deflected, per arrow D (FIG. 2D), via movement of second control member 212, per arrow B (FIG. 2A). The deflection per arrow D translates to outer tube 230 of delivery system 200 and helps to orient distal-most portion 232 thereof so an operator may maneuver system 200 within a patient's venous system for deployment of device 100 to a target implant site like that shown in FIG. 1. With reference to FIG. 2E, once distal-most portion 232 is positioned in proximity to the target implant site, the operator may withdraw outer tube 230 relative to inner member 220 and device 100, per arrow W, via movement of first control member 211 per arrow A (FIG. 2A), in order to engage fixation members 115 of device 100 with tissue at the site.
Methods of use and construction details for exemplary delivery system 200 are described in a commonly assigned United States Patent Application, which has the Pre-grant Publication Number 2013/0079798 (Ser. No. 13/239,990). Furthermore, an alternative exemplary delivery system, similar to a delivery system 300 shown in the plan view of FIG. 3, is described in another commonly assigned United States Patent Application, which has the Ser. No. 14/039,937. In contrast to system 200, outer tube 230 of system 300 is shown including a pre-formed bend 236, and a handle 310 of system 300, as described in the '937 application, contains a stop cock within a sidewall thereof, and further includes a flushing assembly 315. System 300 may be employed to deploy medical device 100 in a similar fashion to that described for system 200. Although delivery systems like systems 200 and 300 have been disclosed and are known in the art, there is still a need for improved assemblies thereof, for example, which accommodate new and improved forms of cardiac pacing devices that are wholly contained within a relatively compact package for implant in close proximity to the pacing site, for example, like medical device 1200, which is described below in conjunction with FIGS. 4A-B.